The present invention relates to a layer sequence built on a substrate in thin-film technology and, more particularly, to a layer sequence comprising an electrically conductive sputtered layer, which is reinforced by a similar electrical conductive reinforcing layer, which is applied to the electrically conductive sputtered layer by a method other than sputtering.
Laser adjustment of resistors has been used for many years to adjust operation and to compensate for manufacturing tolerances in the field of thin-film and thick-film technology. The resistors on substrates or boards are adjusted to their set value, before the substrates or boards are equipped with components, or to a computed resistance value according to the component characteristic values (e.g. capacitance). A slight amount of residue is produced by the adjustment because of the type of material being worked. This residue can be removed, if necessary, after the adjustment by cleaning.
Furthermore for a few years metallic conductive layers (e.g. Gold layers) have been removed or eroded from capacitors, in order to change their capacitance and thus to be able, for example, to adjust the resonance frequencies of oscillator circuits (Lasertrim Capacitors, Johnson Technology, Camarillo, Calif.). This adjustment is also an operational adjustment. Of course extraneous contaminant material is produced during this adjustment procedure near the adjusted locations, but this contaminant material is of little significance for these components in housings, since they are used in connection with adjustable capacitors in the frequency range of up to a few 100 MHz.
However laser adjustment of (metallic conductive) thin-film structures, for example of resonators formed from structured gold on ceramic material (see tuning of ring resonators as described in the still unpublished German Patent Application 198 21 382) is new. Here also an operational adjustment is performed.
During laser erosion of 3 to 5 μm thick gold layers, as often employed in thin-film technology, gold-containing deposits with particle sizes of up to a few tens of micrometers arise. These deposits are very problematical, since open semiconductors (e.g. transistors with 0.25 μm gate structures) are often used in thin-film technology, which are comparatively sensitive to extraneous contaminant material. A cleaning to remove the residue formed by the adjustment is only possible in certain special cases, since the operational adjustment primarily occurs with the components completely assembled on the board or chip. During an adjustment the extraneous deposited particles are only partially removed by vacuuming techniques.